[template] add when/then for functions without results

[ldmonster]

Description

When i use minimock, i want to use When/Then functional for functions without result.
It helps me with checking strict different inputs.

Changes

Before:

We generate When/Then functions only for functions with result

After:

We generate When/Then functions for every functions with or without result

Example

Used struct from minimock repo.

User flow:

ContextAccepter.AcceptContext.When(context.TODO()).Then()
ContextAccepter.AcceptContext.When(context.Background()).Then()

Generated:

// generated same as for functions with result
func (mmAcceptContext *mContextAccepterMockAcceptContext) When(ctx context.Context) *ContextAccepterMockAcceptContextExpectation {
	if mmAcceptContext.mock.funcAcceptContext != nil {
		mmAcceptContext.mock.t.Fatalf("ContextAccepterMock.AcceptContext mock is already set by Set")
	}

	expectation := &ContextAccepterMockAcceptContextExpectation{
		mock:               mmAcceptContext.mock,
		params:             &ContextAccepterMockAcceptContextParams{ctx},
		expectationOrigins: ContextAccepterMockAcceptContextExpectationOrigins{origin: minimock.CallerInfo(1)},
	}
	mmAcceptContext.expectations = append(mmAcceptContext.expectations, expectation)
	return expectation
}

// here's removed input parameters
// this function used to save fluent-style 
func (e *ContextAccepterMockAcceptContextExpectation) Then() *ContextAccepterMock {
        // here's removed working with result
	return e.mock
}